Knife gate valves are commonly used in pneumatic or vacuum conveyance systems that are used to convey various types of dry bulk materials such as grains and other foods as well as non-food materials such as plastics. In order to prevent the leakage of air or vacuum, sealing surfaces must be provided to contact the gate when it is moved to its closed position. These sealing surfaces, even when made of wear resistant materials, must be periodically replaced. In my previous U.S. Pat. No. 4,938,250, I disclosed transverse seals at the rear or aft end of the gate opening which seat against the opposed faces of the gate. These seals can be accessed for inspection and renewal without removing the valve from service. While access to the seals in this manner is highly desirable, the valve still must be removed from service in order to inspect and renew the longitudinal seals and the forward transverse seal. In addition, the valve must be periodically disassembled in order to clean and sterilize the seals and the channels in which they are seated. This cleansing is particularly important and must be frequently performed when the gate valve is used in conjunction with food and drug processing.